Distillation



April I6,l 1935. w. H. BAHLKE Er AL 1,997,675

` DISTILLATION Filed Aug. 28, 1930 2 sheets-sheet 1 william H Bauke.ETT-Lomas E ockdole` April `16, 1935.L

w. H. BAHLKE Er'AL 1,997,675

' DIsTILLATIoN Filed Aug. 28, 195o 2 sheets-Sheet 2 l Y y 7g UCuLLTrL tam zz/ h Invenrs:

CUL'ZZlaTr-L H Bahlke 'y Thomas E Stockdale- Patented Apr. 16, 1935juNirED STATES lATENr oFFlCE "pls'rmLATloN william n. Bahlkeana ThomasE. Stockdale, Hammond, \Ind., assignors to Standard Oil .Company(Indiana), tion of Indiana Application August 28,

Y 14 Clails.

This invention relates t a distillationsystemv wherein the liquid isheated ina closed conduit and .then ashed in a separator, the heatstored in the .liquid being suicient tovaporize a prede- The object ofthis invention is tov reduce the pipe still temperature to which aliquid mustvbe heated in order to vaporize a given fraction there-- Theinvention contemplates the mixing of av non -volatile liquid with acharging stock and heating the mixture in a pipe still whereby theliquid stores enough sensible heat to effect complet'e vaporization of agiven fraction of the charging stock when itis introduced into a flashdrum or separator chamber. The invention is particularly useful in thedistillation of lubricating oils because it affords a means of keepingthe temperature of the oil in the pipe st ill low enough to preventsubstantial cracking. The liquid which is mixed with the charging stockis' preferably a portion of the hot residue from the ash chamber.

In the accompanying drawings wherein similar parts are designated bylike reference characters in the several views,

Figure 1 is a flow sheet -or diagrammatic plan cfa distillation systemfor petroleum hydrocarbons, and

Figure 2 is a detail of said system, showing the relative positions ofthe bubble towers tothe pipe still.

l'Ihe invention will be described as applied to the distillation ofpetroleum, but it isunderstood that the principles of the-invention areapplicable to the distillation of other liquids. In the-system'diagrammatically illustrated in Figure 1, crude oil is heated in pipestill I0, 'gasoline and light ends are flashedv and removed in tower Hat at- ;U mo'spheric pressure, and thev bottoms from this tower aremixed with a non-volatile liquid, passed through other coils in pipestill I0, and nally in troduced into vacuum tower I2, wherein thesensible heat of the liquid causes the complete vaporization andseparation of the lubricating fraction of the oil.

The crudev oil is introduced through pipe I3 to*A yreliux coil I4 inatmospheric tower II. The preheated crude is then conducted through pipeI5, coil I5, pipe II, coil I8, ,pipe I3, heat exchangers Chicago, lll.,a'corpora- 1930Serlal No. 478,340

20, 2I and 22 and pipe 23 tothelower bankof vconvection coilsZI in pipeI0. 'I'he oil is con-l v lducted from these convection coils by pipe28ito the rooftubes 23 in the still and thence by pipe 30 to the base oftheatmospheric tower Il.A Tower Ilmay be vat atmospheric pressure andmay be providedwith suitable baflies and/or'bubble plates inV accordancewith conventional prac-f tice. YThe particular-structure ofthefractionat- Y ing tower forms no part of this invention and'will vnotbe vdescribed in detail. The hot oil is stripped in the base of thetower by steam, introduced through pipe 3|. A light ou cut isremoveafrom y an intermediate ypoint by pipe 32 and a gas oil cut isremoved at a higher intermediate point 33;

3l and'34'-A by. means of steam or hydrocarbon gases. The strippedvapors and gases are regturned tothetower through pipes 32-A and 33--Arespectively.

Gas o il is withdrawn through pipe 35,1v crude preheater 36, pipe '31,'cooler 38 and pipe 39 `to a'suitable storage tank. A part of the gas oilfrom pipe 33er from the storage tank is returned by pump 39a throughpipe 39h to the top of vacuum tower I2 wherein itserves as reux. 'I'helight oil cut is withdrawn from the base of tower 34 and is conductedthroughv pipe 40,' cooler 4I, and pipe. l2 to a suitable storage tank.Gasoline v'apors are removed'from the top of tower I I and are conductedthrough pipe I3, pipe 44, cooler 45 and pipe 45 to a suitable storagetank. A portion of the gasoline is passed through pipe 41 to the upperpart of tower II and is introduced as al refluxover the top bubbleplates.

The residue, ,bottoms or reduced crude is withdrawn from the base oftower Il through pipes I8 and to the' upper bank of convection coils -50of pipe still III.. The hot reduced crude is then passed throughsuitable radiant or wall tubes I, thence pipe 52 and valve 53 into theiiash chamber in the base of vacuum tower I2, which is likewise plates,haines, etc. A heavy oil cut may be taken from an intermediate point oftower I2 through pipe 54 and a medium oil cut may be withdrawn through ahigher intermediate point of pipe 55, both of these cuts being strippedin superimposed strippers 55 and .5E-A, the vapors and gases beingreturned to the tower through pipes 5`A These cuts are stripped insuperimposed strippers v yprovided with suitable bubble.

pipe 63, exchanger 2I and pipe 6I to a. storage tank. A

The non-volatile residue is withdrawn from the base of the tower throughpipe 65. A portion of this residue is conducted by pipe 66 to astripping tower 61 and is therein stripped by steam introduced throughpipe 66. 'I'he steam and vaporized hydrocarbons are conducted by a pipe69 from the stripper to the base of tower I2, Where they are used tostrip the hot reduced crude. Ihe inal residue is withdrawn through pipe10, pump 1I, pipe 12 and exchanger 22, and pipe 13 to a suitable storagetank.

A conduit 1l connects the top of vacuum tower I2 with a booster ejector15, and barometric condenser 16. Water is introduced into the barometriccondenser through pipe 11, and a mixture of water and gas oil iswithdrawn through pipe 18 to a barometric seal 19 from which gas oil iswithdrawn by pipe 80 and'water is withdrawn by pipe 8i. A pipe 82connects barometric condenser 16 with steam ejector 83.

A portion of the residue Yfrom pipe is forced by pump 84 through pipes85 and 49 to the upper bank of convection tubes 50. -This portion of theresidue is called recycle stock and it is heated with the reduced crudein al pipe still for a purpose which will be hereinafter explained.

The operation of our invention may be'briefly described as follows: Thecrude oil is passed through the preheaters and exchangers, and thencethrough the pipe still, where it isheated to about 600 F. It is thenilashedin atmospheric tower II and the'reduced crude is returned to thepipe still, heated to a'temperature of about 730 F. and introduced intothe base of vacuum tower I2. 'I'he absolute pressure at the base of thetower is preferably about 100 mm. and at the top ofthe tower it is aboutmm. The temperatures of the various strippers, coolers, preheaters, etc.form no part of the present invention and willI not 'be described indetail.

When two cuts of lubricating oil are taken from the vacuum tower I2, thetemperature at the base of the tower is preferably about 700 F. If astraight reduced crude is heated in the pipe still and charged into thevacuum tower, the oil must be heated in the pipe still to a temperatureof 760 in order to vaporize the desired fractions at a temperature of'100 at the base ofthe tower. If, on the other hand, an equal volume ofrecycle stock is mixed with the reduced crude, the ilnal temperature inthe pipe still need only be 730'F. to completely vaporize the samefractions in the vacuum tower ata temperature of 700 F. If one part ofthe reduced crude is mixed with two parts of recycle stock, the finaltemperature in the pipe still can be lowered to F., and ii' the ratio ofreduced crude to recycle stock is .1 to .4, the temperature may bereduced to nearly 710 F.

When separating light and heavy fractions (instead of medium and heavyfractions), recycling is still moreieifective in lowering the requiredtemperatures in the pipe still. Mixing two parts of reduced crude withthree parts of recycle lowers the temperature 30; using equal partslowers the temperature 40, and using three parts oi reduced crude toilve of recycle lowers the temperature 50.

These results may be explained as follows, (although we do not limitourselves'to any theory of action): Since the pipe still is operating ata higher pressure than the vacuum tower, a portion at least of the oilwhich itis desired to vaporize remains in liquid form in the pipe still.When it is discharged into the lower part of the vacuum tower, thesensible heat of thev oil must be suiiicient to supply the latent heatrequired for vaporizing the fraction to be distilled; The reduced crudemust be heated to a relatively high temperature in order to supply thissensible heat. By increasing the volume of non-volatile liquid, we makeit possible to supply this sensible heat at lower pipe stilltemperatures. y

While we have described a preferred embodiment of our invention it isunderstood that the invention is'not limited to the distillation ofpetroleum oils or to any of the temperatures,

pressures or other conditions hereinabove set' forth.

The term non-volatile is used herein to dene all liquids which aresubstantially nonvolatile at distillation temperatures and pressures.The recycle stock is non-volatile according to this definition, and itis particularly suitable in our invention, because it'already possessesa considerable amount of heat and because it cannot deleteriouslyail'ect the oil.

When distillation must be carried out at or near the range of crackingtemperatures in the usual type of apparatus, the required temperaturecan be considerably lowered by employing the method of recirculation ofnon-volatile liquid as described above, with consequent reduction inamount of cracking and improvement in yield and quality of distillateobtained.

We claim:

l. In a system for refining petroleum hydrocarbons, an atmospherictower, means for heating crude petroleum and for introducing the hotpetroleum into said tower, means for fractionating it into gasoline, gasoil, light oil and reduced crude, means for heating the reduced crude,means for introducing the hot reduced crude into a vacuum tower, meansfor fractionating said reduced crude into lubricating oil and residue,means for mixing a part of saidresidue with said reduced crude beforesaid reduced crude is passed through said second heating means, andmeans for returning gas oil from' the atmospheric system to serve as areilux near the top of the vacuum tower.

'2. The method of continuously dstilling lubricating oils withoutsubstantial cracking, which comprises heating a conilned stream ofreduced crude in a heating zone, introducing the hot mixture into avacuum zone, and mixing part of the residue from said vacuum zone with 4the stream of reduced crude entering said heating zone whereby thesensible heat of liquids introduced into the vacuum zone is sufficientto supply ,the latent heat of evaporation of the lubricating fraction ofthe oil thereby separating said lubricating fraction from thenon-volatile residue in said vacuum zone.

3. The method of distilling lubricating oils from reduced crudes withoutcracking which comprises admixing about one to four parts ofnon-volatilev hydrocarbons with each part of reduced crude, continuouslyheating the mixture in a stream to a temperature of about 30 to 50'lower than the temperature which would be required in the absence ofadded non-volatile hydrocarbons; flashing the mixture whereby thesensible heat of the added liquids supplies a portion of the latent heatof vaporization of the oils and separately removing vaporizedlubricating oils from the residual liquids.

` 4. A process of continuously refining petroleum hydrocarbons withoutsubstantial cracking therethe heat required to volatilize the desiredparts of the oil being refined .is supplied in part at least by thenon-volatile residue mixed therewith.

5. A process of continuously reiining petroleum hydrocarbons withoutsubstantial cracking thereof, which comprises withdrawing from afracttionating zone .a residue which is substantially non-volatile underthe conditions of pressure and temperature prevailing in said zone,mixing said residue vwith reduced crude containing a vaporizablelubricating oil fraction, passing said mixture "in a coniined streamthrough a heating zone under a pressure greater than that in thefractionating zone and heating saidf mixture to a temperature at whichno'substantial cracking takes place and which is below that temperatureat which vaporization would take place in the absence of added residue,introducing said heated mixture under vacuum into the fractionating zonewhereby the heat required to volatilize a lubricating fraction from thereduced crude is supplied in a large part at least by the non-volatileresidue mixed therewith.

6. A continuous process of refining a reduced crude oil which compriseswithdrawing from a vacuum zone a residue which is substantiallynonvolatile under the conditions of pressure and temperature prevailingin said zone, mixing from one to'four parts of said residue with eachpart of reduced crude to be refined, passing said mixture in a confinedstream through a heating zone and heating said mixture to a temperaturewhich is below that temperature at which vaporization would take placein the absence of added residue and at which no substantialcrackingtakes place, introducing said heated mixture into the vacuumzone and flashing the mixture therein, whereby the heat required tovolatilize the' lubricating fractions of the reduced crude is suppliedin a large part by the non-volatilel residue mixed therewith.

'7. A method of recovering oils from petroleum bottoms containingasphalt which consists in adding to the original bottoms a quantity ofasphalt having high heat storage capacity, heating the mixture,continuously admitting the heated mixture into a vaporizing zone incounter-current with steam to vaporize the oils by the heat stored inthe mixture, the quantity of added asphalt being sufficient to maintainthe temperature against depression to a point below which Vaporizationcannot continue, until'substantially complete vaporization of the oilshas been effected.

8. A method of separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage' medium, heating the mixture, and admitting the heatedmixture into a vapon'z# ing zone in counter-current with steam, thequantity of asphalt added being sufficient to supply the heat ofvaporization of the oils without excessive depression of temperature.

9. A method of recovering oils from petroleum bottoms containing asphaltwhich consists in adding to the original bottoms a quantity of asphalthaving high heat storage capacity, heating the mixture, continuouslyadmitting the heated mixture into a vaporizing zone maintained undervacuum to vaporize the oils by the heat stored in the mixture, thequantity oi added asphalt being suflicient to maintain the temperatureagainst depression to a point below which vaporization cannot continue,until substantially complete vaporization of the oils has been eiected.

10. A method of separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heating the mixture, and'admitting the heatedmixture into a vaporizing zone maintained under vacuum, the quantity ofasphalt added being suiiicient to supply the heat of vaporization of theoils without excessive depression of temperature.

ll. A method ot separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heating the mixture, admittingthe heated mixtureinto a vaporizing zone maintained under vacuum, the quantity of asphaltadded being suflicient to supply the heat of vaporization of the oilswithout excessive depression of temperature, withdrawing asphalt fromthe vaporizing zone, and recirculating aV part of the asphalt Withdrawnto serve as the heat storage medium to be mixed with the originalbottoms.

l2. A method of separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heating the mixture, admitting the heated mixtureinto a vaporizing zone in counter-current with steam, the quantity ofasphalt added being sufficient to supply the heat of vaporization of theoils without excessive depression of temperature, withdrawing asphaltfrom the vaporizing zone, and recirculating a part of the asphaltWithdrawn to serve as the heat storage medium to be mixed with theoriginal bottoms.

13. A process of continuously refining a reduced crude oil whichcontains a desired vaporizable fraction, which comprises continuouslymixing said reduced crude with a residue, such as asphalt, which issubstantially non-volatile under the conditions of heat and pressure towhich the mixture is subjected, passing said mixture in a confinedstream through a heating zone, heating said mixture to a temperaturewhich is below that at which vaporization would take place in theabsence of added residue and at which no substantial cracking takesplace, introducing said heated mixture into a. vacuum zone andseparating the desired vaporizable fraction from the nonvolatile residueby ashing the mixture in said vacuum zone, the heat required to vaporizethe vaporizable fraction being supplied in a large part by thenon-volatile residue mixed therewith.

14. A process as defined in claim 13, in which steam is introduced intothe vacuum zone to assist in separating the vaporizable fraction fromthe non-volatile residue.

WILLIAM H. BAHLKE. THOMAS E. STOCKDALE.

